Arrangement for high precision cylindrical or plane grinding



3, 1969 B. M. BERNELIN ETAL 3,468,072

ARRANGEMENT FOR HIGH PRECISION CYLINDRICAL OR PLANE GRINDING 4Sheets-Sheet 1 Filed Sept. 7. 1966 IN VENT ORS BSEEQNARD MARCEL BERQELINBASTIEN FRINDEL- CLAUDE BENEZECH 3 AT TOR EYS Sept. 23, 1969 BERNELIN ETAL 3,468,072

ARRANGEMENT FOR HIGH PRECISION CYLINDRICAL OR PLANE GRINDING 4Sheets-Sheet 2 Filed Sept. 7. 1966 Y" W I 3:: BY CL INVENTOR 5 mm Mmvtndrawn as I'll Fan/08L auac. l z/vzzzcl/ 3 Mom ATTORNEYS v Sept. 23, 1969B. M. BERNELIN ET AL 3,468,072

ARRANGEMENT FOR HIGH PRECISION CYLINDRICAL OR PLANE GRINDING Filed Sept.7. 1966 4 Sheets-Sheet 3 ATTORNEY$ ARRANGEMENT FOR HIGH PRECISIONCYLINDRICAL OR PLANE GRINDING 4 Sheets-Sheet 4 Filed Sept. 7. 1966IWENTOR drum n: nun. Bnug u Szaasr/s/v Fewer;

United States Patent US. Cl. 51-165 14 Claims ABSTRACT OF THE DISCLOSUREA cylindrical grinding machine having a stationary base with fivebearing surfaces. Two of the surfaces are on one side of the V-shapedguide, two on the other side and a fifth is parallel to the edge wherethe base of the V-shaped guide meets. A slide is mounted on the base,the slide having a grinding wheel.

The present application is a continuation-in-part of copendingapplication Ser. No. 319,744, filed Oct. 29, 1963 now abandoned.

The present invention relates to high precision cylindrical or planegrinding, and more particularly to an arrangement for guiding a slidecarrying either the workpiece or a grinding wheel with respect to theother of the workpiece or grinding wheel mounted upon a stationary base.

Present day grinding machines are able to machine workpieces with amaximum precision of the order of one micron. However, in numerousapplications it was recognized that this order of precision wasinsufficient and that the precision should be improved to about onetenthof a micron. The structure proposed for attaining such precisiongrinding has been cumbersome and complex and has generally beenunsatisfactory in operation.

It is therefore an object of the present invention to provide animproved high precision, cylindrical or plane grinding machine.

Another object of the invention is to provide a guiding system for aslide capable of rectilinear movement upon the base of a high precisiongrinding machine.

In one aspect of the invention, there is provided a stationary basehaving five bearing surface planes formed thereon. Two of these bearingsurface planes are positioned on structure defining a first plane andtwo further bearing surface planes on structures defining a secondplane. These first and second planes form a V-shaped guideway andintersect to form an edge which is parallel to the plane containing thefifth bearing surface plane. The bearing surface planes on the Vguideway are opposed from each other. A slide is mounted on the base forrectilinear movement thereon and may have convex bearing surfaces forsupporting the slide upon the bearing surface planes. A grinding wheelor a workpiece may be carried on the slide. A table is also movablymounted on said base and carries the other workpiece or wheel.

The bearing surface planes may comprise elements which are of hardermaterial than the slide or base and which are inserted in the surfacesof the base. These surfaces may be of silicon. Also the elements mayhave a coating of molybdenum disulfide. The bearing surface planes mayalso comprise locally ground areas on the base surfaces or protrusionscast integrally with the base and then ground to the desired dimensions.

As a further modification, the bearing surface planes may be formed ofquartz discs retained on plates by suction with the plates beingadjustably mounted on a portion of the base. The slide may have agenerally T-shape with the arms being formed of tubular membersfabricated from thin sheets of titanium.

Other objects, advantages and features of the invention will becomeapparent from the accompanying description and drawings which are merelyexemplary.

In the drawings:

FIG. 1 is a schematic side view of the guiding arrangement of thepresent invention;

FIG. 2 is an elevational view of the arrangement shown in FIG. 1;

FIG. 3 is a perspective view of the stationary base illustrated in FIGS.1 and 2;

FIGS. 4 and 5 are diagrams illustrating the geometric relationshipsbetween the workpiece and grinding wheel according to the invention;

FIG. 6 is a top plan view of a T-shaped slide employed in one embodimentof the invention taken along the line 66 of FIG. 7;

FIG. 7 is a side elevational view of a grinding machine embodying theinvention;

FIG. 8 is a front elevational view of the grinding machine of FIG. 7;

FIG. 9 is an elevational view showing the quartz discs being supportedon a portion of the base with several of the elements being partiallyshown in section; and

FIG. 10 is an overall perspective view of the slide illustrated in FIG.6.

Referring to the drawings wherein like reference symbols indicate thesame parts throughout the various views, there will be described indetail a specific embodiment and modifications of the present invention.

Referring to FIGS. 1 through 3, there is shown a stationary base 1 whichhas bearing surface planes 2, 3, 4 and 5 provided on the plane faces 6and 7 which are positioned to form a V-shaped guide with the plane facesintersecting at 13. A fifth bearing surface plane is formed on the upperface of stationary base -1. These bearing surface planes are machinedapproximately to within one tenth of a micron or better and fixedlymounted on the base.

Slidably mounted upon the base is a slide 9 having on its lower face 2spherical or convex bearing surfaces 10 which rest upon bearing surfaceplanes 2 and 3. There are additional spherical elements 11 on slide 9which rest upon bearing surface planes 4 and 5 and a further sphericalelement 12 resting upon the bearing surface plane 8. As may be seen inFIG. 3, bearing surface planes 2 and 4 are opposed from each other and,similarly, planes 3 and 5 are so positioned.

In order for the slide 9 to be capable of rectilinear motion, the planesurfaces 2 and 3 must be parallel to each other, plane surfaces 4 and 5parallel to each other, and the intersecting edge 13 parallel to theplane 8. With this construction, the translation vector of slide 9 isparallel to intersecting edge 13.

A table 14 is movably mounted on slide 9 and is adapted to remove anyfaults in parallelism between the rotational axis of workpiece 15 andthe rectilinear movement axis of slide 9. The axis of rotation ofworkpiece 15 is defined by the center points 16 and 17 which support theworkpiece. A motor 18 is suitably connected to pin or point 17 to rotatethe workpiece at a relatively low speed of one revolution per second,for example. A grinding wheel 19 is positioned on a portion of themachine, to be described later, so as to be in operative relationshipwith workpiece 15. Fine adjustment of the position of the workpiece canbe achieved by the supports or center pieces 16 and 17 in a well knownmanner, while a cross adjustment may be obtained by employing a diflenential screw.

While not disclosed herein, it is apparent that the machine must beprovided with conventional adjusting members to move the table alongvertical and horizontal planes as well as in the plane of the table inorder to adjust the parallel relationship of the rotational axis of theworkpiece and the translation axis of the slide.

ADJUSTMENT IN THE VERTICAL PLANE Let 5 be an angle formed by the axis ofrotation of the workpiece 15 and the translation axis of slide 9 in thevertical plane.

FIG. 4 shows that, if r is the radius of one end of the cone, r-l-Ar theradius of the other end, I the length of the cone and R the radius ofthe grinding wheel 19, then:

OTV W -l-FM ADJUSTMENT IN THE HORIZONTAL PLANE FIG. 5 shows clearly thatif a is the angle formed between the axis of rotation of the cone andthe axis of movement of the slide in the horizontal plane, maintainingthe rotations as above for the remaining values, then:

If Ar micron, then:

In conclusion, in order to suppress the conicity, an extremely accurateadjustment of table 14 must be carried out in the horizontal plane.

Referring to FIGS. 6 through 10, there is illustrated a grinding machineembodying the principles of the invention as shown in FIGS. 1 through 5.In this embodiment, the bearing surface planes comprise quartz studs ordiscs 21, 22, 23 and 24 positioned in V-arranged planes so that disc 21is parallel to disc 23 and disc 22 is parallel to disc 24. It has beenfound that by using quartz, a very hard and stable material, it ispossible to obtain almost perfect planes with the grinding processesused in the optical industry. The surface of such planes, however, issomewhat limited by the nature of the support. For example, with acircular surface 120 mm. in diameter, it is possible to obtain a planeof perfection of the order of 0.01 micron.

In order to provide precise contact between the perfect planes describedabove and an object, such as a slide, the slide must be provided withconvex contacts which may be spherical or toroidal in shape. In FIG. 6,there is generally indicated a slide 25 in the shape of a T having atransverse bar 25a having at its ends circular contact members 26 and26', the peripheral rims of which have a semicircular cross section tocontact studs 21 to 24.

The stem of the slide is indicated at 25b and has an adjusting screw 27at its extreme end having a spherical point which rests upon a similarquartz stud or disc 28. As a result of this contact arrangement, theslide 25 can move upon the optical planes formed by the studs 21 through24 and 28.

As may be seen in FIGS. 7 and 8, the slide 25 described above is mountedupon a machine having a frame 29 composed of square tubing forming arigid unit, the tubing being reinforced by heat treating. The studs ordiscs 21 through 24 and 28, described above, are mounted upon frame 29.In order to provide for rectilinear movement of slide 25, the planecontaining discs 21 and 23 and the plane containing discs 22 and 24intersect to form an edge which is parallel to the plane of disc 28.Each disc described above is mounted upon the stationary frame 29 in anisostatic manner by a mounting which insures a rigid connection, isremovable, and does not deform the optical glass of the discs.

Referring to FIG. 9, disc 22, for example, is mounted precisely on threespherical supports 30 carried by a plate 31 in which there is a duct 32connected to a flexible tube 33 which leads to a vacuum tank (notshown). Small ducts 34- lead from duct 32 and open onto the surface ofthe disc near supports 30. A toroidal joint 35- is provided around eachsupport 30, and this joint together with a suitable lubricant provide aseal so that disc 22 is retained in position by a vacuum produced by thevacuum tank.

The plate 31 may be inclined with respect to the axis of rotationdefined by the balls 36, and accurate adjustment of the plate may beobtained by the combination of a diiferential screw 37 and a mechanicalreduction. The mechanical reduction may comprise an intermediate plate38 having on its lower surface a V-groove in which are received twoballs 39 resting in a second V-groove parallel to the first groove, thesecond groove being formed in a plate 40 integral with frame 29. Theupper surface of plate 38 supports two balls 41 which are retained in aV-groove formed in plate 31 and upon which the plate can pivot at thesame time the plate pivots on balls 36 by means of arms 42, the ends ofsaid arms being notched to receive balls 36. The balls 36 are seated ina second V-groove formed in member 40, upon which member the sphericalend of screw 37 rests.

This same mounting having multiple but parallel axes of rotation is alsoused for discs 21 through 24.

Disc 28 may be mounted on two plane members 43 and 44 shown in FIGS. 6and 7 which have perpendicular pivoting axes A5 and AS, with thesemembers being adjustable by means of screws 47 and 48, respectively.

Slide 25 also has a vertical arm 250 at the base of which is mounted thegrinding assembly comprising grinding wheel 19 and its drive motor 48-coaxial therewith.

Slide 25 is preferably fabricated from tubular members formed by weldingthin sheets of titanium having a thickness less than 1 mm. Thisparticular structure virtually eliminates any deformation of the slide,with the physical and mechanical properties of alloyed or unalloyedtitanium insuring stability, rigidity and light weight of the slide.

The adjusting screw 27 on slide 25 permits a small degree of movement ofthe grinding wheel in a plane perpendicular to the rotational axis ofthe grinding wheel. In a specific embodiment, the drive motor may rotateat a speed of 24,000 r.p.m. with the outside diameter of the grindingwheel being about 40 millimeters.

Slide 25 may be given a translation movement by a second slide 50mounted thereabove. The slide 50 rolls upon two rails 51 and 51' havingcircular sections by means of two grooved rollers 52 and 52 and acylindrical roller 53, the three rollers forming a triangle. The rails51 and 51 are mounted upon frame 29 by means of a ball joint 54 at oneend and by means of two balls 55 at the other end, balls 55 beingcarried by plate 56 which is mounted for angular adjustment by means ofa differential screw 57.

A wheel 58 is mounted beneath slide 50 and has a cylindrical nut 59pivotally mounted therein with screw 60 passing therethrough and rotatedby motor 61 through a speed reducer. A fork 62 extends downwardly fromslide 50 to straddle stem 25b of slide 25 to provide a drivingconnection.

Slide 50 also carries a grooved pulley 63 over which is passed ametallic cable 64 having one end attached to stem 25b by means of aslidably mounted member 65-. The other end of cable 64 is connected by aspring 66 to a element 67. This arrangement permits adjustment of thetraction exerted on stem 25b in order to support a portion of the weightof slide 25 so as to insure precise contact between the slide and thediscs and to avoid deterioration of the discs and the contact points ofthe slide.

The workpiece 15 is carried by a work-supporting unit comprising threelarge tables. The first table 68 is carried by frame 29 by means of tworails 69 and 69', one end of each rail being supported by socket joint70 and the other end by two balls 71 carried by an element 71' which ispivotally mounted on ball 72 and adjustably by means of screw 73.

On one side of table 68 there are provided V-shaped guides 74 and at theother side a flat member 75, with the member 74 slidably mounted on rail69 and flat member 75 slidably mounted on rail 69. The sliding movementof table 68 is controlled by a fine differential screw 76.

A second table 77 rests upon table 68 by means of two spherical contacts78 and a ball 79. A differential screw 80 having a micrometricadjustment moves table 77 parallel with respect to table 68. Thisadjustment permits precise horizontal positioning of the workpiece so asto obtain the desired cylindrical or conical shape.

A third table 83 is mounted upon table 77 by means of balls 81 and adifferential adjusting screw 82. The center points 16 and 17 and a motorfor slowly rotating workpiece 15 are mounted upon table 83. Actuation ofscrew 82 permits vertical alignment of the axis of rotation of theworkpiece parallel to the axis of movement of slide 25.

Tailstock 16 is provided with a device which exerts constant pressurecontrolled by a comparator 84 on the end of workpiece 15.

It is apparent that the accuracy of the movement of the arrangement asdescribed above depends primarily on the accuracy with which the bearingplane surfaces are ground and positioned. The positioning of each discwill next be described using as an example the adjustment of the bearingsurface planes 21 through 24 which are arranged in the V-shapedguideway.

With respect to disc 22 as illustrated in FIG. 9', which is exemplary ofthe mounting of the discs, it will be seen that:

with on being the angle at which the optical plane of the disc rotateswith respect to the axis of ball 36 and H being the displacement ofscrew 37.

In the adjustment procedure, the first step is to position the opticalplanes of discs 21 and 22 parallel to each other and then to adjustplanes 23 and 24 into parallel relationship. This adjustment is possibleby means of screws 37 which have difierential threads so as to causedisc 21 to pivot about the axis A1 and disc 22 to pivot about the axisA2. The axis A1 is at right angles to axis A2. With this arrangement, itis possible to obtain a parallelism to within two to five microradians.

The same procedure is then carried out for discs 23 and 24 by pivotingthese about their respective axes A3 and A4.

In the second step, disc 28 is adjusted so as to be parallel to theintersection of the planes defined by discs 21 and 23 and to theintersection of the plane defined by discs 22 and 24. Because of thepreceding adjustment, these intersections are parallel to each other. Itis thus only necessary to position these two intersections and discs 28horizontally with the horizontal plane being chosen for ease of controland such control being capable of a very high level of precision. Inorder to obtain the two above described horizontal intersections, themachine may be pivoted with the aid of adjustable feet provided withdifferential screws and mounted on the stationary frame.

The disc 28 is horizontally adjusted by means of the micrometer screws47 and 48 which have differential threads so as to pivot disc 28 aboutthe axes A5 and A'5.

The adjusting arrangement of the structure disclosed herein enables thesecond step of adjustment to be carried out to within a fewmicroradians.

The structure of the present invention may be provided with adjustingmechanisms which are well known in the art for positioning the workpieceduring the grinding operation. This positioning may be carried outeither by optical, mechanical or electronic means.

Thus it can be seen that the present invention has provided a mountingarrangement for a grinding machine by means of which high precisioncylindrical or plane grinding may be obtained.

It is to be understood that changes can be made in the various detailsof construction and arrangement of parts without departing from thespirit of the invention, except as defined in the appended claims.

What is claimed is:

1. In a high precision cylindrical grinding machine, the combination ofa stationary base, means on said base for defining five bearing surfaceplanes, including means on said base for defining first and secondplanes with said planes forming a V and intersecting to form an edge,two of said bearing surface planes being on said first plane and afurther two bearing surface planes being on said second plane, the twobearing surface planes on said first plane being opposed from the twobearing surface planes on said second plane, said fifth bearing surfaceplane being parallel to said edge, a slide mounted on said base forrectilinear movement thereon and having convex bearing surfaces bearingupon said bearing surface planes, a grinding wheel on said slide, and atable movably mounted on said base for carrying a workpiece thereon forpositioning in operative relation with respect to said grinding wheel.

2. A cylindrical grinding machine according to claim 1 wherein saidbearing surface planes comprise elements inserted in said first andsecond planes, said elements being of a material harder than said slideand base.

3. A cylindrical grinding machine according to claim 2 wherein saidelements are made of silicon plates.

4. A cylindrical grinding machine according to claim 2 wherein saidelements have a coating of molybdenum disulfide.

5. A cylindrical grinding machine according to claim 1 wherein saidbearing surface planes comprise protrusions cast with the respectiveplanes and having the bearing surface ground.

6. A cylindrical grinding machine according to claim 1 wherein saidfifth bearing surface plane comprises a locally ground area on saidbase.

7. A cylindrical grinding machine according to claim 1 wherein saidconvex bearing surfaces are integral with said slide.

'8. A cylindrical grinding machine according to claim 1 wherein saidconvex bearing surfaces are on the lower face of said slide.

9. A cylindrical grinding machine according to claim 1 wherein saidconvex bearing surfaces comprise ball elements retained in said slide.

10. A cylindrical grinding machine according to claim 7 wherein saidbearing surface planes are formed of quartz discs having opticallyground bases.

11. A cylindrical grinding machine according to claim 10 and furtherincluding plates on said base supporting said quartz discs, suctionmeans on said plates for retaining said quartz discs thereon, and anadjusting screw having a spherical end carried by said plate, saidspherical end resting upon a portion of said base, and a pair ofspherical contacts between said plate and said portion of said base forsupporting said plate thereon.

12. A cylindrical grinding machine according to claim 1 wherein saidslide is a tubular structure comprising thin sheets of titanium.

13. A cylindrical grinding machine according to claim 12 wherein saidtitanium sheets have a thickness no greater than one millimeter.

14. A cylindrical grinding machine according to claim 1 wherein saidslide has an arm and a difierential screw carried by said arm, saiddifferential screw having a spherical end resting upon said fifthbearing surface plane, said differential screw being so positioned thatadjustment thereof will move said grinding wheel in a plane parallel toa transverse plane of said wheel.

References Cited UNITED STATES PATENTS Mitchel 51-165 X Guyer 3086Parkes 308--3 Harley.

Dall 51-165 Klint et al. 308240 US. Cl. X.R.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION mum: Nm jugjfjgyyg Dated September 23, 1969 nvnntoflfl flgrnq rq M. [1911115111f-lgba stjan Efrjndel, and .ClfllLdB Beneztach It is certified thaterror appears in the above-identified patent 1nd that said LettersPatent are hereby corrected as shown below:

Column 3, line 23, insert "Q after "tan SIGNED ANU SEALED DEC 2 W D LuauMamba, WILLIAM E. suaunme, JR. m Qnnissioner of Patents 5 33 UNITEDSTATES PATENT OFFICE CERTIFICATE OF CORRECTION 3 Q Patent: No. j A bUOK: Dated .zestembcr 5 1 39 I fx-zrnaird higrcel ifirt' e "|i'r'Fr-hegtjm', imjni Gian-(3e B-zanezech It is certified that errorappears in the above-identified patent and that said Letters Patent arehereby corrected as shown below:

In the heading, line 1 4, "60,661" should be --i 0,66

SIGNED AND SEALED (SEAL) Attest:

Edward LLI-ImbaJF. mum-m E. Eastman, in. i I g Officcr comissipner ofPatents

